Solenoid operated pumps for handling volatile liquids, such as aqueous ammonia, are inefficient because they are not true positive displacement pumps. Rather, such pumps meter the amount of liquid by adjusting the length of the stroke, which is a long procedure. Also, when gas bubbles form in the intake tube the pump discharges a varying amount of liquid due to the compression and expansion of the gas bubbles thereby preventing accurate metering of the liquid to be fed to the developer unit.
Further, because such pumps move relatively small quantities of the liquid, or ammonia, and have a built-in tendency to heat up due to the electromagnetic coil, thereby exposing the ammonia to temperatures above its boiling point, the ammonia begins to boil and the pump fails to function.
Air operated pumps, designed normally to run at relatively high piston speeds, are also known and attempts have been made to alter such pumps for use in feeding aqueous ammonia to a diazo process reproduction machine. Because such a pump requires modification to considerably slow down the piston speed, to permit pumping a reduced amount of ammonia, the valves becom inefficient to the point where they no longer open and close properly unless they are immersed in fluid. Subsequently, when the pump input line and pump chamber are void of ammonia, as would be the case with initial machine start-up, the system is not able to pump the ammonia from the bottle to the pump chamber.
Additionally, such a modified air operated pump results in the ammonia and water solution saturating the piston seal. Once the piston seal is saturated the unit is not capable of generating either a vacuum or pressure cycle due to leakage of air around the piston seal.
For the foregoing reasons, presently available pumps and metering devices currently in use for handling fluids such as aqueous ammonia are ineffective and unreliable in use. Applicants ae unaware of any commercially available or prior art device which meets the rigid requirements of a device for pumping and precisely metering the rate of feed of aqueous ammonia from a supply container to a developer unit of a diazo process reproduction machine.